Circuit arrangement for producing a saw-tooth current in inductance coils



1949 J. HAANTJES EI'AL 2,489,375

CIRCUIT-ARRANGEMENT FOR PRODUCING A SAWTOOTH CURRENT IN INDUCTANCE COILS Filed May s, 1947 HAANT'JES'& J.J.P VAL ETON J [NVENTORS W Q M 11 AGENT Patented Nov. 29, 1949 2,489,375 CIRCUIT ARRANGEMENT FOR PRODUCING A SAW-TOOTH COILS Johan Haantjes and 305 Eindhoven, Netherlan National Bank and T Conn., as trustee Application May 8, 1947,

In the Netherlands May 10,

7 Claims.

The invention relates to a circuit-arrangement for producing a saw-tooth current in an inductance coil exhibiting both inductance and resistance with the aid of a pulse-like voltage this voltage having a, constant value between the pulses and for a longer time period than the duration of each pulse. Circuit-arrangements of this kind are used, for example, for deflecting cathode-rays in cathode-ray tubes, the coil being used as a deflecting coil. In this case the pulse-like voltage may, for example, be obtained from the secondary of a transformer, the primary of which is included in the output circuit of a time-base generator, this generator being designed such that during the fly-back of the saw-tooth current of the generator avoltage of constant value is set up across the primary, and thus also across the secondary, of the transformer.

In view of the use of such circuit-arrangements, it is generally desirable that the sawtooth current produced in the coil should vary linearly with time during the fly-back. However, owing to the presence of the resistance in the coil, this will not be the case. If, for example, a direct current voltage having a magnitude E is abruptly applied to such a coil, the coil has set up in it a current t=time, L=inductance of the coil, r=resistance of the coil. As revealed by progression development, the deviation from straight line relationship is, in this case, proportional to the exponent and to the time duration of the period of sawtooth current.

The time duration of the period is generally prescribed, and

CURRENT IN INDUCTANCE u Jean Philippe Valeton, ds, assignors to Hartford rust Company, Hartford,

Serial No. 746,694

cannot be made arbitrarily small, since this entails higher cost, and a given size is necessary for use in view of available space and permissible dimensions.

The object of the invention is to provide a circuit-arrangement, in which the deviation from linearity of the saw-tooth current is considerably smaller than in the well-known circuit-arrangements. The invention is based on recognition of the fact that this deviation is primarily due to phase distortion for the various frequencies of the components into which the voltage applied in a pulse-like fashion can be broken down.

If the voltage applied is decomposed into sinusoidal components, the current i passing through the coil would be ideally equal to of this factor, which is most essential for the deviation from linearity, is practically equal to Zero for high frequencies. For low frequencies, for example the fundamental frequency of the saw-tooth current, the tangent has a comparatively large value. If, for example, use is made to the accompanying drawing, in which Figs. 1

3 4 and 2 illustrate a circuit-arrangement of the said This ensures a further reduction of the value of kind and the pulse-like voltage supplied thereto tan g). respectively. Figure 3 is a modification of Fig- The optimum effect of the circuit-arrangement ure 1. The circuit-arrangement shown in Fig. 1 is obtained if, according to a further embodiment comprises the series combination of a coil l com- 5 of the circuit-arrangement accordin to the inprising inductance designated L1 and resistance vention, provision is also for the coils l and 2 designated 11, and a parallel circuit, of which one to be such that the condition: branch includes a coil 2 comprising inductance designated L2 and resistance designated T2, and L2 L2 the other branch a coil 3 comprisin inductance 10 designated L and resistance designated 1. A pulse-like voltage having the shape illustrated in is fu1fiued F 2 1S supphed the Input .r If this condition is fulfilled, a minimum value ThlS voltage is constituted by periodical pulses found. fortan (p at lower Values of w. on com gs gi iz g f ig s; g gf z g gfi ig sidering the expression found above for tan (1),

- v i s r V. i n ritten in th for f to which exceeds ii. A voltage of this kind can be Wh ch ca be W e m 0 produced in a number of ways which are not of interest to the present invention. 7 tan If this voltage is assumed to be. composed of sinusoidal components and if in the circuit-arrangement shown in Fig. 1 currents ii, i2 and 2' in which a, b, c and d are simplified functions flow in Coils 2 and 3 respectively the follow; of the inductances and resistances, it is found mg relations p for each Value w: for high values of w to approach Zero, owing to the presence of the term comprising (0 in the +7 -ldenominator of the fraction. At smaller w, the i(7'+j L)=i (1' +j L term comprising m in the numerator is very important. The coefiicient b is now equal to: Z1=Z2+Z It follows, after some reduction: r1L2 +r1LL2+rL1L2+1'L2 -1'2L1L i X[ jw7' Lcu LLg T71+7'7"2+7172 (T2L+TL2+T2L1+TL1 +T1L2+T1L) (.02LL2+L1L2) solving for the tangent of the phase angle, of If this coefiicient is assumed to be zero, the. the factor between brackets which introduces the above indicated condition is found. undesired distortion, Assuming L1= L2=2L and 11: 1, from r1 2 "2 1 2 "1 z +71LL2 l 2 ii z -f 712L111) w(7 1 L T22L1+ T2214 TTgL 7'7'1L2) 0J3 (Ll/1L2 L Lg LL22) As above derived, if the pulse-like voltage is which, it follows that 1'2: 161, if the tan (p is cal-- directly applied to the coil. L, r, a tangent ofthe 40 culated for the coil 3 at which phase-angle equal to tan g0= l tan m 7 1000 wL a value of is found. Thus, in order to reduce phase distor- 1 tion, tan must always be smaller than tan 1. 3840 A further explanation of the value found for tanz indication that tanqv will, in actual fact, alis found for an angular velocity of w of 6.10' ways be smaller than tan (731, if the conditions are radius per second, that is to say approximately satisfied that 64 times smaller than in the case of direct supply of this voltage to the coil. The values of r T and L may be in ohms and henries. This ref is larger than I 65 sults in a considerably improved approximation 2 of the straight-line relationship of the saw tooth current. also According to a further, favourable embodiment r1 T of the circuit-arrangement according to the inf 15 Smaller thall j' fi; 60 vention in Fig. 3, a capacity 02 is included in the parallel branch in series with an auxiliary coil 2.. This capacit ma .be expressed in faradsv The first condition indicates that the quality of Arfhrther improvemint the shlape of the coil 2 composed of L2 and m which is connected tooth current can thus be ensuredsaid improve in parallel with the coil 3 composed of L and r 5 ment being a maximum if must have a lower figure of merit than the latter.

According to a further embodiment of the cir- LL1 cult-arrangement the coil l, composed of L1, 11 2=Wm is such that 2 1 2 1 2 r1 7 Those parts of the circuit-arrangement which is smaller than correspond to parts of the circuit-arrangement shown in Fig. 1 are designated by like referencenumerals. so that the figure of merit of the series-con- For this circuit-arrangement also, a calcula nected coil is higher than that-of the coil L, r. tion similar to the preceding permits of calculating the current i'passing through the coil 3 for a given value of w it being again found that times a factor which introduces the distortion. It is found that the tangent of the phase-angle of this factor can be reduced again, if the previously derived conditions are fulfilled. presence of the capacity permits, however, of also making sure that the absolute value of the factor itself varies only to a small extent throughout the entire frequency range. The optimum condition is ensured if the capacity C2 is adjusted to the above-indicated value.

An illustrative example of values for the circuit shown in Fig. 3 may be given as follows:

L=3 henries L1=3 X 10 henries L2=-3 x 10- henries 1:3 ohms T1=0Q31 ohm r2=3360 ohms Cz=2280 ,ua farads What we claim is:

1. A circuit-arrangement for producing a sawtooth current in an inductance coil exhibiting an inductance L and a resistance 1', including a pulse-like voltage which exhibits a constant value between the pulses and for a longer time than the duration of each pulse, wherein this pulse-like voltage is fed to a circuit, said circuit comprising the series combination of an auxiliary coil exhibiting an inductance L1 and a resistance 1'1 and a parallel circuit, of which one branch includes the inductance coil (L, r) and the other branch an auxiliary coil exhibiting an inductance L2 and a resistance 12, and these auxiliary coils being of such value that I2 1'. L2 is greater than L and - 2. 1s smaller than Z+2L2 3. A circuit arrangement to produce sawtooth electric variations in an inductance coil having an inductance designated L and a resistance component 1 comprising, a source of alternating current having a stepped wave shape, a first auxiliary coil having an inductance L1 and a resistance component 11, a second auxiliary coil having an inductance L2 and a resistance component r2, said second auxiliary coil coupled in parallel with the inductance coil, said source of desired signals supplied to a series connection of the said first auxiliary coil and the parallel coupling of the inductance coil and the said second auxiliary coil, and said first and second auxiliary coils having values with respect to the said inductance coil at which is smaller than L and V L 1 IL L, L 2L,

where 1, 1'1, and rz=resistance in ohms L, L1 and Lz=inductance in henries 4. A circuit arrangement to produce sawtooth electric variations in an inductance coil having an inductance designated L and a resistance component 1' comprising, a source of alternating current having a stepped wave shape, a first auxiliary coil having an inductance L1 and a resistance component 11, a second auxiliary coil having an inductance L2 and a resistance component 1'2, said second auxiliary coil coupled in parallel with the inductance coil, said source of desired signals supplied to a series connection of the said first auxiliary coil and the parallel coupling of the inductance coil and the said second auxiliary coil, and said first and second auxiliary coils having values with respect to the said inductance coil at which and where r, 11 and rz=resistance in ohms L, L1 and Lz=inductance in henries 5. A circuit arrangement to produce sawtooth electric variations in an inductance coil having an inductance designated L and a resistance component 1 comprising, a source of alternating current having a stepped wave shape, a first auxiliary coil having an inductance L1 and a resistance component 11, a second auxiliary coil having an inductance L2 and a resistance component r2, said second auxiliary coil coupled in parallel with the inductance coil, said source of desired signals supplied to a series connection of the said first auxiliary coil and the parallel coupling of the inductance coil and the said second auxiliary coil, and said first and second auxiliary coils having values with respect to the said inductance coil at which 1', T1 and r2=resistance in ohms L, L1 and L2=inductance in henries 6. A circuit arrangement to produce sawtooth electric variations in an inductance coil having an inductance designated L and a resistance component r comprising, a source of alternating current having a stepped wave shape, a first auxiliary coil having an inductance L1 and a resistance component 11, a second auxiliary coil having an inductance L2 and a resistance component T2, a capacitive element in series with the said second auxiliary coil, said second auxiliary coil and capacitive element coupled in parallel with the inductance coil, said source of desired signals sup,- plied to a series connection of the said first auxiliary coil and the parallel coupling of the inductance coil and the said second auxiliary coil and capacitive element, and said first and sec- 0nd auxiliary coils having values with respect to the said inductance coil at which 1 L L2 L and 11 1 n. Z1 L+2L2 where r, 1 1 and r2=resistance in ohms L, L1 and La=inductance in henries and capacitive element coupled in parallel with the. inductance coil, said: source of desired signals supplied to a series connection of the said first auxiliary coil and the parallel coupling of the inductance coil and the said second auxiliary coil, and said first and second auxiliary coils and capacitive element having values with respect to the said inductance coil at which 1, n and r2=resistancein ohms L, L1 and Lz=inductance inhenries, and Cz=capacity in farads JOHAN HAANTJES. v

JOSUE JEAN PHILIPPE VALETON.

No references cited. 

